An image forming apparatus capable of minimizing color mis-registration due to runout of gears is disclosed. The image forming apparatus includes a plurality of photosensitive bodies having transfer points to transfer images onto a transfer object, a driving source to drive at least two photosensitive bodies of the plurality of photosensitive bodies, and a driving gear train to transmit driving power from the driving source to the at least two photosensitive bodies. The driving gear train includes photosensitive body shaft gears respectively connected to the photosensitive bodies driven by the driving source, and connecting gears to transmit the driving power to the photosensitive body shaft gears. When any one of the photosensitive body shaft gears is set to a reference photosensitive body shaft gear, the number of teeth of the connecting gear, which is disposed at a jth position from the reference photosensitive body shaft gear, is determined so that a value calculated from the following equation is substantially an integer. L π ⁢ ⁢ D · 1 R j Here, D refers to a diameter of each of the photosensitive bodies, L refers to a distance between the transfer points of two adjacent photosensitive bodies, and Rj refers to a speed reduction ratio from the jth connecting gear to the reference photosensitive body shaft gear.